A variety of methods for detecting target biomolecule in a sample have been developed. Among those methods, the method using nanopore is a bio-pore imitation system, which is in the spotlight as a DNA detection system with high-sensitivity and also as a sequencing tool in the future.
There are many DNA detection systems using the nanopore. For example, U.S. Pat. No. 6,428,959 discloses methods of determining the presence of double stranded nucleic acids in a fluid sample by measuring, while translocating nucleic acids in the sample through a nanopore, an amplitude of current flowing through the nanopore and then blockading the current.
U.S. Patent Application Publication No. 2004/0144658 describes an apparatus and method for biopolymer identification during translocation through a nanopore, which detects a translocating biopolymer with a nanopore based on the concept that in case where a bias potential is ramped across both electrodes, the increase of current passing over a barrier occurs when the carrier energy sequentially matches with the conduction band energies of the translocating biopolymer.
U.S. Patent Application Publication No. 2003/0104428 provides a method for characterization of nucleic acid molecules, in which a greater signal change is accomplished by the modification of specific local area using a protein specific to a nucleotide sequence. This publication discloses a technique of detecting DNA with a specific sequence using nanopores.
However, these conventional methods and apparatuses for detecting DNA using nanopores have problems in that DNA to be detected must have the specific sequence or the structure of apparatuses and the condition for detection are complex, thus rendering the manufacturing process very complicated.
Many efforts have been made to provide nanopores having such a small diameter as bio-pore up to date. In actual, however, the manufacture thereof is quite difficult; and accordingly, a need has existed for a method capable of detecting nucleic acid fragments below 2,000 bps using a nanopore sensor with a diameter ranging from 20 to 120 nm.